This invention pertains to electric lamps and, more particularly, is concerned with electric filament lamps.
The phenomenon of candoluminescence has been known for the last hundred years and was utilized in the so-called "Auer" or "Wellsbach" gas mantle which, when exposed to the heat of a flame, emits light of a color temperature far in excess of the nominal flame temperature. Thus, the insertion of such a mantle into a gas flame provides a visible light level far greater than that characteristic of the flame by itself. Early in the application of the gas mantle a mixture of CeO.sub.2 and 99% ThO.sub.2 was identified as an efficient and effective candoluminescent material.
While the gas mantle has a long history of application, the principle of candoluminescence has been definitively elucidated only recently. It is now believed that candoluminescent material fluoresces when excited by thermal radiation. The emitted radiation for a given temperature is shifted to shorter wavelengths than would be expected from the ideal black body distribution to provide a greater percentage of visible light at a given temperature and, correspondingly, less energy supplied to the emitting medium to maintain the radiator at a temperature to provide the same black body intensity in the visible.
The utilization of a candoluminescent medium to change incandescent spectral energy distribution and, therefore, the increasing efficacy of an incandescent source would provide major savings in energy resources.